Finally, let's discuss why the superlattice in the \(c\)  direction was not
detected by other techniques. In the introduction to this paper we have
presented several techniques which have permitted he observation of the CO.
However, only few of them such as \(^{13}\) C NMR or neutron scattering, have the
spectral or spatial resolution to detect the interchain CO modulation. In the
case of \(^{13}\) C NMR, the main CO was detected by observing the splitting of
\(^{13}\) C NMR lines but, as seen in Fig. 2 and 4 of Ref [1]},
this splitting is very small. It is not surprising that a modulation of the CO
would lead to a second separation of each line too tiny to be resolved. The
measurement of the displacement of the counter anions responsible for the CO was
a challenging neutron scattering experiment [2]}. The
modulation of the displacement would just be included in the error bars. In our
case the observation of the CO modulation was possible because of : (i)
The low P\(_1\)  symmetry which allows the rotation of the g-tensor axes. In higher
symmetry, this effect would not exist. (ii) The very small linewidth of
the organic salts (\(\Delta H\sim 1\)  G) allows to resolve the two EPR lines.
(iii) The two EPR lines are not collapsed by the interchain exchange
interaction because electronic correlations in the \(c\)  direction were nearly
absent and the magnetic field was high (exchange splitting
regime[3]}).
